From the state of the art (EP 11 46 322 B1), seals for scales are known. These are used for the temporary sealing of the scale housing, usually for the purpose of cleaning. Here, a seal that is, for example, inflatable, is activated between a load receiver projecting out from the scale housing and the housing itself, so that the (annular) gap is closed between the load receiver and housing, in order to prevent the penetration of cleaning agent. In the deactivated state, the seal releases the load receiver, so that this can forward a weight force introduced into it without force shunts to a weighing sensor that is arranged in the housing and that has, e.g., a strain gauge or that operates according to the principle of electromagnetic force compensation. The charging of the seal with the medium to be fed (e.g., compressed air) is structurally complicated and expensive.
From WO 2007/050145 a seal for a scale is known in which a sealing element that can be moved relative to the scale housing can be moved under spring loading against a flange arranged on the upper end of the load receiver. Through contact with this flange, the annular gap between the load receiver and housing is sealed against the surroundings. For opening the seal, the moving element is lowered by pressure loading against the spring force, wherein the load receiver is released for supporting its weighing function.
Disadvantageously, for this seal, the load receiver is loaded with a spring force that is (considerable under some circumstances) introduced directly into the weighing sensor. The corresponding mechanism is loaded accordingly, which can also lead to overloading of individual components or regions of the weighing sensor or the scale. Undesired creep effects could be the result. Also, an electromagnetic compensation of this force introduced into the sensor could be undesired and could require, under some circumstances, high compensation currents.
In particular, the sealing effect depends on the contact pressure of the sealing surfaces against each other, so that a high sealing effect necessarily accompanies a high loading of the weighing sensor or the scale mechanism.